1. Field of the Invention
The present invention relates to an optical glass, a shapable glass material for press-shaping, an optical element and a process for producing the optical element. More specifically, it relates to an optical glass that has high-refractivity and high-dispersion properties and that is less colored, a shapable glass material made of the optical glass for press-shaping, an optical element made of the optical glass and a process for producing the optical element.
2. Related Art Statement
In recent years, there are increasing demands for optical glass having high-refractivity and high-dispersion properties. As such a glass, there is known an optical glass having a phosphate-based glass composition as a base material and containing a relatively large amount of components for providing a high refractive index, such as TiO2 and the like. (for example, see JP-A-6-345481)
However, the above glass contains a relatively large amount of components for providing a high refractive index such as TiO2 and the like while having a phosphate-base glass composition as a base, and as a result, the glass is liable to be colored and has a problem from the viewpoint of a color degree. In the invention of the above JP-A-6-345481, attempts are made to heat-treat the optical glass for improving the glass in coloring. In this case, however, a heat-treatment step is required, and the production procedure inevitably comes to be complicated. Further, there is a problem that it is difficult to impart the entire glass with a uniform color degree.